Apparatus for processing resin

ABSTRACT

Apparatus including an elongated mill structure having a cooling jacket wherein a resin is fed from a resin kettle directly to the mill structure in a molten state, wherein it is forced down the structure and along the structure&#39;&#39;s cool periphery to lower the temperature of the resin to its brittle temperature, and wherein the hardened resin is broken into particles of desired shape and size as a finished product.

United States Patent 1 Bailey 51 Sept. 4, 1973 APPARATUS FOR PROCESSINGRESIN [76] Inventor: Wesley T. Bailey, 700 Cloyden Rd.,

Palos Verdes Estates, Calif. 90274 [22] Filed: Mar. 8, 1971 [21] Appl.No.: 122,036

[52] U.S. CL. 241/65, 425/202, 425/310 [51] Int. Cl. B29b 1/03, B29f3/02, B29f 3/08 [58] Field of Search 241/23, 65, 101 B, 241/247; 425/6,202, 310', 264/5, 28, 140,

[56] References Cited UNITED STATES PATENTS Dedn'cks et al 62/320Bludeau Jarvis 241/65 X Furnace Fuel in 1/1960 Beike et al 241/65 X2/1971 lrving 18/12 TS Primary ExaminerRobert L. SpruillAttorney-S0kolski & Wohlgemuth and John Holtrichter, Jr.

[ 5 7 ABSTRACT Apparatus including an elongated mill structure having acooling jacket wherein a resin is fed from a resin kettle directly tothe mill structure in a molten state, wherein it is forced down thestructure and along the structures cool periphery to lower thetemperature of the resin to its brittle temperature, and wherein thehardened resin is broken into particles of desired shape and size as afinished product.

9 Claims, 3 Drawing Figures memenscr" 4m 3356518 IVUIUI Wesley T. Boiley;

INVENTOR.

ATTORNEY.

Furnace Fuel In APPARATUS FOR PROCESSING RESIN BACKGROUND OF THEINVENTION The background of the invention will be set forth in twoparts.

1. Field of the Invention The present invention pertains generally tothe field of resin processing and more particularly to the field ofprocessing what are commonly called hard resins and thermoplasticresins.

2. Description of the Prior Art The milling of plastic material andparticularly of thermoplastic and hard resins is well known in the art.The milling procedure is used to provide improved physical propertiesfor the shaped articles formed after this process. For example, millinghelps prevent surface deterioration of shaped articles such as sheets,films and molded articles. Also, there are many instances where it isdesired that the material be in the form of fine particles or particlesof certain sizes and shapes. As an example, fine particles ofthermoplastic material may be advantageously used in a powdered resincoating process wherein a continuous film is formed on an articlewithout the use of a solvent. This is generally accomplished by an airsuspension of the particles. The article to be coated is heated, andwhen it is immersed in the suspended particles, the article will beuniformly covered and no pollution of the air will have taken placesince this is a solvent-less process. This process is known in theindustry as fluidized bed coang".

In the past, thermoplastic and hard resins have required different typesof processes. This is because these two types of materials have rathersignificantly different temperature related characteristics. Forexample, thermoplastics have a melting point above ambient temperatureand a brittle point or secondary order of transition below ambient. Onthe other hand, hard resins have a melting point above ambient and abrittle point below the melting point but above ambient. For a morecomplete description of these materials, their compositions,characteristics and known processes used therewith, reference may bemade to a book by Brage Golding entitled POLYMERS AND RESlNS, D. VanNorstrand C., Inc., Princeton, New Jersey, 1959, and to other relatedtexts.

Not only have the processes used with these materials been different butthey also have had severe limitations and disadvantages. In the area ofthermoplastics, very expensive and intricate closed" systems requiringvapor pressure control have been used. For example, in one such system,plastic material is milled in an enclosed system wherein the liquidvapor pressure is varied while the plastic is in contact with a. boilingliquid, which has a boiling point substantially corresponding to themelting point of the plastic material at the liquid vapor pressure underwhich the system is operating.

in another technique, the thermoplastic material is first processed intoparticles of generally relatively large size and irregular shape byother processes such as described above, before being deposited in a dryhopper and then being chilled to well below the materials brittletemperature by spraying with a liquid refrigerant such as liquidnitrogen immediately prior to a grinding process accomplished underslight superatmospheric pressure. This process and the one describedimmediately before clearly show that a new and improved process notrequiring more than a single step and not requiring elaborate and veryexpensive equipment would constitute a significant advancement of theart.

With respect to what are generally considered hard resin processes, theresin is polymerized with heat in a large resin kettle, and after beingdehydrated, the molten resin is quickly run out of the kettle onto acooling floor, which is generally a concrete slab or it may beconstructed of sheet iron plates welded together to form a smoothsurface. Once the resin has cooled to a brittle solid, it is manuallybroken up with sledge hammers into pieces which are thereaftertransported to another site and ground to a coarse powder and thenpossibly pulverized in an impact mill. Again, it is clear that theseprior art techniques lead to undesired oxidation and fumes and impuritycontamination. Also, these processes are very costly, time consuming,and result in a final product which usually contains too many fines",small particles which are undesirable for dust and other handlingreasons.

SUMMARY OF THE INVENTION ln view of the foregoing factors and conditionscharacteristic of the prior art, it is a primary object of the presentinvention to provide a new and improved apparatus and technique forprocessing resins, not subject to the disadvantages enumerated above.

It is another object of the present invention to provide a method forprocessing in a single continuous step either thermoplastic or hardresins to provide a finished particulate product.

It is still another object of the present invention to provide apparatusfor processing resin in which the resin so processed is not contaminatedby condensed moisture or impurities and is not subject to oxidation, andwhich does not require a completely closed system with elaborate vaporpressure control.

According to the present invention, apparatus for continuouslyprocessing resins to a finished particulate product immediately from asource of molten resin is provided which includes an elongated carrierhaving an entrance end and an exit end, and feed means operativelycoupled to the entrance end of the carrier for transporting resins in amolten state from a source of such resin to the carrier. Disposed aboutthe periphery of the carrier is a means for lowering the temperature ofthe resin within the carrier from the resin melting point to its brittlepoint. The invention also includes grinding means including a drivengrinding element disposed within the carrier for moving the resin in itsmolten state both toward the exit end and toward the carrier's peripheryto cool the resin and make it solid, and by its grinding actionproducing and reducing the size of particles of resin ejected at theexit end of the carrier.

The invention may include apparatus to cool the resin to its brittletemperature above ambient, as in the case of hard resins, or it mayinclude refrigeration apparatus which will bring the temperature of theresin to its brittle temperature below ambient when working withthermoplastic resins. Also, the exit end of the carrier' may be providedwith an orifice fixture which determines the final size and shape of theparticulate output.

The features of the present invention which are believed to be novel areset forth with particularity in the appended claims. The presentinvention, both as to its organization and manner of operation, togetherwith further objects and advantages thereof, may thus be understood bymaking reference to the following description taken in conjunction withthe accompanying drawings in which like reference characters refer tolike components in the several views.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic illustration ofapparatus for processing resins in accordance with the presentinvention;

FIG. 2 is a sectional view taken along line 22 of FIG. 1; and

FIG. 3 is a schematic diagram of apparatus constructed in accordancewith another embodiment of the present invention.

DESCRIPTION OF THE INVENTION With reference again to the drawing andmore particularly to FIG. 1, there is shown apparatus 11 forcontinuously processing resins to a finished particulate productimmediately from a source of molten resin. The apparatus 11 includes anelongated carrier or tube 13 having a coolant jacket 15 about itsperiphery 16. The tube 13 also includes an entrance end 17, an exit end19, and a grinding element 20, disposed within the tube. The grindingelement is shown in FIG. 1 mechanically driven by a variable speedelectric motor 21 through a conventional gearing arrangement 23. Theelement 20 is preferably of the Archimedes screw type which has theadvantage of moving the material to be ground toward the tubes peripheryas well as downstream toward the exit end thereof.

The coolant jacket 15 in this embodiment is provided with an inlet port25 and an outlet port 26, both being connected by piping to aconventional coolant system (not shown), having a capacity to reduce thetemperature of the material within the tube 13 by a desired amount. Forexample, where a hard resin" is heated to at least its melting point(about 360F) in a conventional resin kettle 27 by a heating system 29connected to a source of fuel (not shown) and allowed to flow in itsrnolten condition by opening a valve 31 in a discharge line 33 betweenthe kettle 27 and the tubes entrance end 17, the resin will follow thepath indicated by arrow 35 into the tube 13 where the grinding element19 will convey it generally downstream and also toward the coolantjacket 15. Here the periphery of the tube is cooled by cold waterflowing through the jacket 15 and the resins will be caused to changefrom a liquid state to a solid state within the tube as its temperaturereaches the brittle point. The grinding element 20 then not onlytransports the now solid material downstream, but also breaks up thesolid resin into a desired final saleable form, and which leaves theapparatus 11 as indicated by arrow 37.

The grinding action of the element or screw 20 may provide the desiredsize of particulate product by itself, or, a desired product size andshape may be accomplished by the screw 20 and tube 13 in conjunctionwith an orifice fixture 39 mounted at the tubes exit end 19. The orificefixture 39 may have a single round hole, or it may have, as shown inFIG. 2, a plurality of holes 41 of any desired shape and size. Thefixture also functions with the screw 20 to hold back and recycleparticles reaching it which are too large.

The fixed parameters of the apparatus 1 1, such as the grinding elementssize and pitch and the size and shape of the apertures in the orificefixture, provide major determinations as to the characteristic of thedevice's output 37. However, the type and temperature of the coolantused and its flow rate as well as the speed of the screw 19 are factorswhich provide the apparatus 11 with a very great degree ofcontrollability for any particular resin and for any of many types ofresin. For example, the cooling means may be a refrigeration unit (notshown) which causes a conventional refrigerant liquid or a gas such asFreon to flow through the coolant jacket 15. In this way, thermoplasticmaterials which have a brittle point below ambient may be processed in amanner similar to that for hard resins.

In another embodiment 50 of the invention as illustrated in FIG. 3, theshaft 51 of a grinding screw 53 is directly coupled to a variable speedelectric motor 55 mounted at a first end 57 of an elongated housing ortube 59. The shaft 51 is supported at the first end 57 by a bearing 61,at its downstream end 63 by a bearing 65 in a second end wall 67, andapproximately at its center 69 by a center bearing 71 supportedcoaxially with respect to the tube 59 by a center wall 73.

The peripheral wall 75 of the tube 59 is surrounded by a cooling jacket77 having a pair of coolant inlets 79 and a pair of coolant outlets 81communicating with the coolant jackets interior 83 in which a coolant 85flows. As in the first embodiment, the type of coolant may be chosenwhich will sufficiently cool within the tube 59 a particular moltenresin to its brittle point, the resin going through a conduit 87 from aresin kettle such as kettle 27 as indicated by arrow 89. A pump 91 maybe coupled into the conduit pipe 87 by conventional means such as aflange 93 to aid the resin flow 89 from the kettle into the interior 95of the tube 59 occupied by the revolving grinding screw 53.

The operation of the apparatus 50 is similar to that of the firstembodiment described, in that the moltenresin is cooled, solidified andground within the tube 59. However, here an orifice arrangementincluding one or more apertures 97 in the end wall 67 and an aperturedcutter 99 is mounted by any conventional means to the downstream end 63of the shaft 51 just outside of the end wall 67. The particulatefinished product may then be transported by a conventional conveyor belt101 to a convenient location for packaging or use, or it can bedeposited directly into a container 103.

It can be seen from the foregoing that the invention provides a veryeconomical, simple, yet effective method of producing a finishedparticulate product in a single step by processing liquid resin directlyfrom a resin kettle and the like. It should also be noted that there isno opportunity for the processed resin to become contaminated byimpurities or water vapor, or oxidized.

There are many large volume resins now being sold which are stillproduced by the same archaic hand method developed many years ago. Theseinclude the phenolic resins, isophthalic polyester resins, and hardresins" which are a group of resins in large volume includingrosin-maleic, styrene-maleic, which are often used as a major ingredientin floor polishes. Also, as noted above, the group of resins known asthermoplastic resins may also be advantageously processed by theinvention herein described without the use of very elaborate and costlyprocessing systems heretofore thought to be necessary to produce aparticulate product.

The materials used to fabricate the invention are not critical and anymaterial generally considered suitable for similar functions may beutilized. Also, devices and components may be substituted for thosespecifically identified where similar functions are provided.

It should therefore be evident that, although the invention has beendescribed in several embodiments, it is susceptible to modification andother embodiments. Accordingly, it is intended that the foregoingdisclosure and drawings shall be considered only as illustrations of theprinciples of the invention.

What is claimed is:

1. An improvement in apparatus utilizing an elongate mill structure withan elongate grinding element coaxially rotatably mounted in an elongatecarrier having entrance and exit ends, wherein the improvementcomprises:

resin kettle means including a resin kettle for heating resins to amolten state;

feed means including a kettle discharge line disposed between andcommunicating with said resin kettle and said entrance end of saidcarrier for transporting resins in a molten state from said resin kettlemeans to said carrier;

cooling means disposed about the periphery of said carrier for loweringthe temperature of resin within said carrier from its melting point toits brittle point; and

grinding means including means driving said grinding element for movingresin in its molten state both toward said exit end of said carrier andtowards said periphery thereof to be cooled and made solid, and forcontinuously producing and reducing the size of particles of resinejected as a finished particulate product at said exit end of saidcarrier.

2. The improvement according to claim 1, wherein said grinding meansalso includes a variable speed motor mechanically coupled to saidelongate grinding element.

3. The improvement according to claim 1, wherein said feed means alsoincludes valve means in said discharge line for controlling the flow ofsaid molten resin.

4. An improvement according to claim 1, wherein said grinding element isan Archimedes screw, and wherein said cooling means includes a coolantjacket disposed about said carrier, said jacket including intake andoutlet port means for operationally coupling to said coolant jacket acoolant.

5. The improvement according to claim 1, wherein said grinding meansfurther includes an orifice fixture disposed at said exit end of saidcarrier, said fixture including an orifice configuration determining thesize and shape of the hardened resin particles furnished as saidfinished particulate product. i

6. The improvement according to claim 5, wherein said orifice fixtureincludes an apertured cutter mounted on the downstream end of saidelongate grinding element.

7. The improvement according to claim 1, further comprising conveyormeans disposed adjacent said exit end of said elongated carrier fortransporting said finished particulate product to a predeterminedlocation.

8. The improvement according to claim 4, wherein said coolant is at atemperature lowering the temperature of resin within said carrier to itsbrittle point above ambient.

9. The improvement according to claim 4, wherein said coolant isrefrigerated to a temperature lowering the temperature of resin withinsaid carrier to its brittle point.

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1. An improvement in apparatus utilizing an elongate mill structure withan elongate grinding element coaxially rotatably mounted in an elongatecarrier having entrance and exit ends, wherein the improvementcomprises: resin kettle means including a resin kettle for heatingresins to a molten state; feed means including a kettle discharge linedisposed between and communicating with said resin kettle and saidentrance end of said carrier for transporting resins in a molten statefrom said resin kettle means to said carrier; cooling means disposedabout the periphery of said carrier for lowering the temperature ofresiN within said carrier from its melting point to its brittle point;and grinding means including means driving said grinding element formoving resin in its molten state both toward said exit end of saidcarrier and towards said periphery thereof to be cooled and made solid,and for continuously producing and reducing the size of particles ofresin ejected as a finished particulate product at said exit end of saidcarrier.
 2. The improvement according to claim 1, wherein said grindingmeans also includes a variable speed motor mechanically coupled to saidelongate grinding element.
 3. The improvement according to claim 1,wherein said feed means also includes valve means in said discharge linefor controlling the flow of said molten resin.
 4. An improvementaccording to claim 1, wherein said grinding element is an Archimedesscrew, and wherein said cooling means includes a coolant jacket disposedabout said carrier, said jacket including intake and outlet port meansfor operationally coupling to said coolant jacket a coolant.
 5. Theimprovement according to claim 1, wherein said grinding means furtherincludes an orifice fixture disposed at said exit end of said carrier,said fixture including an orifice configuration determining the size andshape of the hardened resin particles furnished as said finishedparticulate product.
 6. The improvement according to claim 5, whereinsaid orifice fixture includes an apertured cutter mounted on thedownstream end of said elongate grinding element.
 7. The improvementaccording to claim 1, further comprising conveyor means disposedadjacent said exit end of said elongated carrier for transporting saidfinished particulate product to a predetermined location.
 8. Theimprovement according to claim 4, wherein said coolant is at atemperature lowering the temperature of resin within said carrier to itsbrittle point above ambient.
 9. The improvement according to claim 4,wherein said coolant is refrigerated to a temperature lowering thetemperature of resin within said carrier to its brittle point.